In an ink-jetting recording apparatus such as an ink-jetting printer or an ink-jetting plotter (a kind of liquid ejecting apparatus), a recording head (head) can move in a main scanning direction, and a recording paper (a kind of recording medium) can move in a sub-scanning direction perpendicular to the main scanning direction. While the recording head moves in the main scanning direction, a drop of ink can be ejected from a nozzle of the recording head onto the recording paper. Thus, an image including a character or the like can be recorded on the recording paper. For example, the drop of ink can be ejected by causing a pressure chamber communicating with the nozzle to expand and/or contract.
The pressure chamber may be caused to expand and/or contract, for example by utilizing deformation of a piezoelectric vibrating member. In such a recording head, the piezoelectric vibrating member can be deformed based on a supplied driving-pulse in order to change a volume of the pressure chamber. When the volume of the pressure chamber is changed, a pressure of the ink in the pressure chamber may be changed. Then, the drop of ink is ejected from the nozzle.
In such a recording apparatus, a driving signal consisting of a series of a plurality of driving-pulses is generated. On the other hand, printing data including level data (gradation data) can be transmitted to the recording head. Then, based on the transmitted printing data, only necessary one or more driving-pulses are selected from the driving signal and supplied to the piezoelectric vibrating member. Thus, a volume of the ink ejected from the nozzle may be changed based on the level data.
In detail, for example, an ink-jetting printer may be used with four level data including: a level data 00 for no dot, a level data 01 for a small dot, a level data 10 for a middle dot and a level data 11 for a large dot. In the case, respective volumes of the ink corresponding to the respective level data may be ejected.
In order to achieve the above four level control, for example, a driving signal as shown in FIG. 7 may be used. As shown in FIG. 7, the driving signal is a periodical signal of a recording period PATA. In one period thereof, the driving signal includes a first pulse signal PAPS1 appearing in a term PAT1, a second pulse signal PAPS2 appearing in a term PAT2 and a third pulse signal PAPS3 appearing in a term PAT3.
In the case, the first pulse signal PAPS1 forms a first driving pulse PADP1, the second pulse signal PAPS2 forms a second driving pulse PADP2, and the third pulse signal PAPS3 forms a third driving pulse PADP3.
The first driving pulse PADP1, the second driving pulse PADP2 and the third pulse signal PAPS3 have a common (the same) waveform. Each of the first driving pulse PADP1, the second driving pulse PADP2 and the third driving pulse PADP3 can eject a drop of the ink alone. That is, when each of the driving pulses is supplied to a piezoelectric vibrating member, a drop of the ink, whose volume corresponds to a small dot, is ejected from a nozzle.
In the case, as shown in FIG. 8, a level (gradation) control can be achieved by increasing or decreasing the number of driving pulses to be supplied to the piezoelectric vibrating member. For example, when a driving pulse is supplied thereto, a small dot may be recorded; when two driving pulses are supplied thereto, a middle dot may be recorded; and when three driving pulses are supplied thereto, a large dot may be recorded.
In addition, a diameter of a dot to be recorded can be variably controlled by changing a waveform of a driving pulse. For example, according to a driving method disclosed in JP Laid-Open Publication No. Hei 10-81012, as shown in FIG. 9, the second pulse corresponding to a recording for a small dot is smaller than the first pulse and the third pulse.
Furthermore, it has been proposed that two driving signals are prepared in advance. For example, as shown in FIG. 10, according to technique disclosed in JP Laid-Open Publication No. 2003-182075, the first driving signal COMA and the second driving signal COMB are used selectively. This technique can make the driving operation much faster.